I suggest a developmental system (DS) approach for discussing scientific progress in research into epigenetic inheritance (EI). This framework combines the systems biology approach of Conrad Waddington for investigating embryological development with the sociological approach of Ludwik Fleck for analysing the development of scientific systems. The contribution of EI to a discussion of progress in biology is chosen as a case study because of its problematic nature: the results stemming from this research programme are seen as unimportant by followers of the traditional, Modern Synthesis (MS) version of evolutionary theory, while the same results are seen as crucial and progressive by biologists who are developing a new, revised version of evolutionary theory, known as the Extended Evolutionary Synthesis (EES). The EI case study therefore highlights the context-sensitive nature of assessments of scientific progress during periods of theory change and suggests that progress is relative to the delineation of the theoretical boundaries of the scientific system and the time scale that is chosen.